Oscillation generator



Patented `Aug. 28, 1945 UNITED s'rlrl'lias,1 A.'|'F.1-1'1r'; carica i I oscm'rrnaaaroa Kurt Schlesinger, West Lafayette, Ind., assignmto Radi tion oIDelawnre o Comration of America, a corpora- Application March 4, 1942, Serial No. 433,290 40mm, (C1. 25o-'36) rangement and construction, which is easy to 'Ihis invention is directed to oscillation generators and particularly to oscillation generators of the character where it` ls desired to generate and develop linear or the so-called saw tooth voltage waves of substantial amplitude.

Among the objects and advantages of the invention are those providing an oscillation generator which is relatively simple in its arrangements and in which the' developed output voltage shall be completely linearly increasing with time, and in which it is relatively easy to control either or both the frequency of the developed energy or the amplitude thereof.

The oscillator of the type herein to be described is broadly what is known as a I"sawtoothoscillator wherein the amplitude of the developed energy increases (or decreases) with time at a relatively slow rate, and wherein the amplitude of the output energy, after reaching a predetermined value, is reduced (or increased) to the minimum (or maximum, as the case may ling speciiicatlon and claims in connection with the accompanying drawing, in which,

Figure 1- is a diagrammatic representation of one form of circuit for developing saw-tooth waves according to the invention;

Figure 2 is a, modication of the output of the arrangement shown by Figure 1 showing a modification of the coupling of the oscillator to speaking, the invention herein to be described is one of a type wherein the rapidity with which the energy output is reduced to a minimum value is substantially of the order of that substantially instantaneous change obtained in a gaseous discharge tube, although the invention herein to be described is particularly applicable to the sO-called hard tube'in which the characteristics remain substantially uniform at all times. as contrasted with the variable characteristics of the so-called gaseous discharge tubes.

Broadly speaking, the invention herein to be described is closely related to the circuit disclosed and claimed in a co-pending application.

of the same inventor led concurrently herewith and entitled Frequency divider, Serial No. 433,289. The present invention, therefore, has as one of its main objects that of providing a circuit for generating saw-tooth wa'ves. It also has as one 0f its primary objects that of providing a, relatively simple circuit for generating saw-tooth waves which are completely linear in their characteristics. A further object of this invention is to provide a saw-tooth wave generator wherein the developed sawtooth wave uniformly changes from a minimum value of voltage to a predetermined maximum amplitude value at a. relatively slow rate and then collapses to reach again the predetermined minimum value at a relatively rapid rate.

A further object and advantage of the inven- -tion isto provide a circuit for developing sawtooth waves which is relatively simple in itsI arthe output system; and

Figure 3 is a still further modiiication show? ing D. C. output coupling to a load circuit such as the magnetic delecting coils of a cathode ray tube.

Now referring to the drawing for a further understanding of the invention there is provided a vacuum tube which may, when desired, be of the type known in .the art as the 6N? or within the eld of view of this invention the various instrumentalities incorporated within the tube may equally well be embodied in two completely separate tube envelopes. flrst half of the tube assuming the tube to be of the so-called 6N7 type, comprises the cathode I3, the control electrode |5 and the anode I1, while the second half comprises the rectly to the high voltage terminal 33 by way of conductor 35, while the anode or plate element |1 is preferably connected to the same high voltage line through a resistor element 31, and also connects from connecting point 39 by way of the potentiometer 4| to ground at 25.

At the tapping point 45 on the potentiometera connection is made through the conductor 41 to the control electrode 2| of the second half of the tube Il, so that output energy from the plate |1 may be supplied to control electrode 2|. The control electrode |5 connects to one of the condensers 50, 5|, 52 or 53 which are adapted to be connected individually in circuit by the switch contact sweep arm connecting to ground at 25.

The condensers 50, 5|, 52 and 53 are individually Thel - tubes.

trode 93 connected to the terminal point 4I at which the resistor 51 connects with the individual condensers 59, 5|, 52 and 53 and by way of the lswitch arm 55 to ground at 25. The cathode of the power amplifier 95 is connected to ground by way of the variable resistor 91, of, preferably,

- non-linear resistance distribution, which has around it the shunt by-pass condenser 68.

assaese of thatrepresentedfor the plate or anode voitage as applied to the conductor 93 which, as illus- In the arrangement shown, the various values suggested for condensers and resistors. as well as the various voltages, are those which haveA proven satisfactory in the loperation of the disclosed invention, although it should be understood that the parameters suggested are illustrated merely by way of example to show one form of operating v system which has proven satisfactory.

In such an arrangement as herein described it is. of course, apparent that the frequency at which the oscillations are developed is determined by adjusting the values of resistors 51 and/or 59 or by varying the values of the condensers connected between terminal point I and ground 25, which may be conveniently accomplished by connecting the switch 55 with'one of the condensers 5l, 5|, 52 and 53. Such changes in frequency may be made without in any way changing the amplitude of the resultant sawtooth wave energy which is developed at the point 9i, as illustrated diagrammatically by the schematic representation of the voltage wave shown immediately above terminal point 9|. On the other hand, by varying the bias voltage applied to the control electrode 2i of the second half of the tube Il by means of adjustment of the tapping point 45 of the potentiometer 4I, a change in frequency may also result. a

'Ihe foregoing action, as herein explained, may be understood substantially from the following description of the circuit operation.

trated, is approximately 20 volts. Under these circumstances. the circuit herein disclosed may Abe used successfully as a driver for the succeeding power amplifier for magnetic or electrostatic scanning. The direct lcoupling shown, for instance, between the point 5I and the control electrode 33v of the power .amplifier 65 is feasible because `the sweep voltage swings between ground and approximately +20 volts with an average value of approximately +10 volts, which may be compensated by the cathode to ground resistor B'I` of the tube Il. v

.From what-has been shown, it is apparent that in general operating conditions it is usually desirable to set the -value of resistance effective betweenthe terminal point 39 and the point 45 at which the control electrode connects to the potentiometer 4I, since the selected value of resistance controls the linearity, as well as the am-` In the disclosed system, the rst half of the tube, in effect, operates essentially like a gasfilled triode and it functions, in general, as thel high vacuum. duplication of such gas-discharge usual types of saw-tooth generator circuit since However, the circuit hereinv demonstrated has a substantial advantage over the the grid or control electrode is completely blocked off and takes no grid current during the charging period of the sweep. As there is no inertia in the circuit at the discharge point," oscillation frequencies as high as 100 kilocycles may easily be obtained. I-

In considering the circuit and its operation, the

l amplitude of the sweep voltage may readily be adjusted, as above stated, by a control or change in the tapping point 45 on the potentiometer 4I which varies the bias voltage applied to the control electrode 2| of the second half of the tube I I.

It is apparent that the more the bias voltage is reduced. the smaller becomes the amplitude of the developed oscillations, while, at the same' l time, the frequency of the generated oscillations increases, so that the product F, Ais always conand Arepresents the amplitude of each developed saw-tooth energy wave. Thus, the linearity factor, H=fCR, may be adjusted permanently so that the linearity is sufficiently good: (M=8) and the amplitude 'sweep voltage, as indicated by the voltage representation of the wave at the point 5I, may easily be made oi the order of about 11s stant`, where F represents the sweep frequency l yplitude, -and then the amplitude may be controlled most easily by varying the value of the cathode resistor" of the -power amplifier tube 65. Also, it can be seen from what has hereinabove been stated, that the resistors 51 and 59 control only the frequency of the saw-tooth, and that the setting of the potentiometer 4I controls only the amplitude of the saw-tooth. Output energy, lwith whatever degree of ampliilcation is desired, maybe derived from the output electrode 69 of the power ampliilertube 65 (or further ampliiler tubes energizedv therefrom) The arrangement shown and disclosed by Figure 2 of the application is essentially the same as that of Figure 1, with the exception that the power amplifier tube 55 is connected by way of a so-called A. C. coupling through the coupling condenser Il and the potentiometer 'I3 'serving with its variable tapping point 'I5 as the coupling vresistor whichapplies varying bias to the tube.

This is substantially the usual form of conventional capacity coupling with the volume control illustrated.

lmagneticdeflection, and thedeiiecting coils 8i and 83 are schematically represented as surrounding the neck of a cathode ray tube '85 which is schematically represented in cross section to show' only the exterior envelope wall. Output ,energyv from the anode 69 of the tube 65 is fed Q to the coil 83, which is in turn connected to the coil-8l` which connects to the positive terminal of 'the power supply. The arrangement of Figure 3 is slightly modiiled with respect to that of Figure 1, in that the portion of the potentiometer 4I between the variable tapping point 45 and the connecting point 39 of Figure l is represented in Figure 3 as the point 43'. The portion of the potentiometer between the tapping'point 45 and ground 25 in Figure 1 is represented in Figure 3 by the resistance value 4 I Otherwise the circuit connections are essentially as shown and describedin connection with 'Figure 1.

Peaking correction for magnetic deflection is preferably carried out in the plate circuit of the poweram'pliier vby a series resistor, rather than in its grid circuit as shown.

It is, of course, apparent that many and various modifications of the invention here disclosed may be made without departing from either the spirit or the scope of the present invention, and accordingly it is believed that such (modifications as fall fairly within the spirit and scope of what is hereinafter claimed may be readily resorted to.

Having now described my invention, what I claim is: I

1. A saw-tooth wave generator comprising an electron discharge device including a cathode, an anode and a control electrode, an electrical storage element connected between the controll electrode and a predetermined point of fixed potential, means for supplying charging energy at a substantially uniform rate in a positive direction to the storage element, means to bias the cathode of the discharge device relative to the point of iixed potential, to a predetermined amount, a second electron discharge device also including a cathode, a control electrode and an anode, an impedance element connected between the anode of the rst electron discharge device and said point of xed potential, a connection between the second named control electrode and an intermediate point of said impedance element, and a connection between the cathode of the second discharge device and the cathode of the rst discharge device, so that at a time period when the charge acquired by the storage element is equal to the cathode bias, a discharge of the storage element is initiated and the cathode is placed at the potential of the fixed point so as to accelerate the discharge rate of the storage element.

2. `A` saw-tooth wave generator" comprising' an electron discharger device including a cathode, an anode and a control electrode, a resistor element connected between the cathodeand a point of iixed potential to bias the said cathode 4 relative to its anode, an electrical storage element having its terminals directly connected between the control electrode and the said point of xed potential, means for supplying charging energy to said storage element to, charge .the said element at a substantially uniform rate.- a -second electron discharge device -including a cathode, an anode and a control electrode, agalvanic connection between the anode oi' the first electron discharge device and the control electrode of the second electron discharge device Y for providing normally a conductive state in the second electron discharge device and-thereby to bias the first of said devices to an inoperative state by the said cathode bias, a.` direct connection between the cathod elements of each discharge device so that'at the instant when thev rst electron discharge device current ilow in the said second electron discharge device is cut the ltube cathode elements, the cathode of the age element by the current flowl between the control electrode and the cathode of the first electron discharge device.

3. A saw-tooth wave generator comprising a pair of electron discharge devices each including a cathode, an anode and a control electrode, a direct connection between the cathodes .of each of the discharge devices, and a cathode resistor connecting each cathode to apredetermined point of fixed potential to provide a bias for the said discharge devices, an electrical storage element connected between the control electrode of the iirst of said electron discharge devices and the said point of xed potential, means for charging the said storage element substantially linearly in such a direction that a positive potentialrelative to the point of fixed potential isapplied to the terminal of the storage element connected to the said control electrode, means for applying operating voltages to the anodes of each of the said electron discharge devices and for normally maintaining the second of the said discharge devices in an operative state, a resistance element connected between the anode of the iirst of the said electron disy charge devices and the point of fixed potential,

electrode and the cathode of the first electron discharge device' lso that a substantially sawtoothgwave formation is produced across the said storage element, and means for adjusting the connecting point of the control electrode of the `second electron `discharge device to the anode resistor of the rst electron discharge device to vary thereby the amplitude of the developed saw-tooth vol-tage wave across the said storage element.

4. The saw-tooth wave generator claimed in claim 3 comprising, in addition, a power ampliiler stage directly connected across the said storage element, and means for introducing trig- 00- off and, as a result of the direct connection of gering control impulses upon the said `cathode resistor to stabilize thefrequency of the sawtooth wave voltages.`

KURT SCHLESINGER. 

